The hyperspectral instrument DESIS (DLR Earth Sensing Imaging Spectrometer) was installed on the exterior of the International Space Station on 27 August 2018. The German ESA astronaut Alexander Gerst and NASA astronaut Drew Feustel unpacked the instrument on 20 August 2018.

Its view of Earth will be something special: The DESIS hyperspectral instrument has 235 spectral channels to look at our planet and observe the changes in land and water surfaces. On 27 August 2018 at about 21:00 CEST, the instrument developed by the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) and equipped with a robotic arm was taken out of the airlock of the International Space Station (ISS) and installed on the MUSES platform located on the space station's exterior. The hyperspectral data obtained from space is expected to deliver information for environmental monitoring, among other uses. "With this data, for example, we can recognise whether the plants in a field on Earth are in a state of stress at a given point in time from a distance of 400 kilometres," says DLR project manager Uwe Knodt. "This will allow us to look at the world from a new perspective and thereby benefit our society through this view from space."

Farmland, oceans and soil

Several conditions can trigger stress on a plant: insufficient nutrients, unfavourable environmental conditions and an inadequate water supply. The evaluation of DESIS hyperspectral data through sophisticated algorithms will enable conclusions to be drawn in this regard. Farmers, in turn, could benefit from this data from space by learning at an early stage whether their fields must be fertilised in a specific way, and which fertiliser their plants need. The images acquired by the DLR instrument can also provide information on the plants' stage of life, as well as the moisture content of soil and plants. "As a result, the global cultivation of food – and therefore the provision of food – can be optimised," Knodt explains. In addition, the instrument can deliver information on the health of forested areas, identify the mineralogical composition of specific regions, and record the constituent elements and quality of oceans and lakes.

The speed of the images and the flexible angle for viewing Earth from space enable other applications besides resource monitoring and environmental surveillance. These potential uses include humanitarian aid, whereby emergency rescue teams could receive valuable information from space quickly and in a timely manner in the event of a disaster.

The only hyperspectral instrument on the ISS

The spectrometer, which was developed and built at the DLR Institute of Optical Sensor Systems, will be located on the MUSES platform for Earth-observation instruments for a period of five to seven years and will observe our planet around the clock. DLR alone will be able to collect data on 26 million square kilometres of Earth’s surface each year and evaluate a wide range of scientific issues. The commercial licence to use the image data is held by the US industrial partner Teledyne Brown Engineering, which also installed the MUSES instrument platform on the ISS. DESIS will record Earth with a resolution of 30 by 30 metres per pixel in the visible to near-infrared spectrum. It is the first hyperspectral instrument to be installed on the International Space Station.

Fresh data on Earth's dynamic processes

Rupert Müller at DLR's Earth Observation Center (EOC) is responsible for the data processing. A hyperspectral boom is in full swing at the moment, he says. Countries such as Japan and Italy are planning future missions with hyperspectral instruments. Germany is also preparing such a mission with EnMAP, scheduled for launch in 2020. “Presently, the availability of hyperspectral images from space is very limited," Müller says. "DESIS will fill this gap and continuously deliver fresh data on Earth's dynamic processes."

After the successful installation of the instrument, tests will begin to ensure that DESIS is functioning properly after being transported into space and installed on the MUSES platform. The sensitive instrument and its processors must then be calibrated to suit the conditions in space. The next step involves testing the quality and validity of the received data. The engineers and scientists are hoping that DESIS will deliver the first images at the beginning of October 2018.

The DESIS project

DESIS (DLR Earth Sensing Imaging Spectrometer) is a joint project between the German Aerospace Center (DLR) and the U.S. industrial company Teledyne Brown Engineering, which owns the Earth-observation platform known as MUSES (Multiple User System for Earth Sensing). Within the framework of this collaborative arrangement, DESIS is expected to provide DLR with data for scientific purposes, while Teledyne Brown will take responsibility for the commercial part of the hyperspectral data. Two DLR institutes are involved in the project: The Institute of Optical Sensor Systems built the instrument as part of the space segment subproject, while the Earth Observation Center (EOC) in Oberpfaffenhofen is managing the ground segment subproject, which is responsible for the reception of data, its processing and transfer into applications.